, have you had much joy with those planes on plywood? I have had very variable results on solid wood - I avoid them altogether on splintery wood. Also don’t like them for longish runs, not ideal for the handholds in the OP, pliometric box.
Unlike Theo, I hate sanding, so it’s a round over bit for me.
, I am with Charles: the 1/4” gives a nice rounded edge on 3/4” material. Smaller gives a “smoothed” square edge. Perhaps worth trying the El Cheapos in various radii, then buying a better one in the size you prefer. As I stated elsewhere, I use El Cheapos as virtual disposables, but having tried a Lee Valley 1/4” round-over bit, I would buy that quality for frequent, long-term use, as the other guys have said.
By the way, for a 1/4” round-over, a 1/4” shaft should be adequate for most purposes, if price is the issue and you have managed to clean up your collet reducing sleeve.